Hydraulic actuators are utilized for a wide variety of purposes. In order to operate a hydraulic actuator, a hydraulic system including a hydraulic pump, tubing and additional controls is generally required. For example, aircraft utilize hydraulic actuators to perform various functions. By way of an example, some aircraft may include a thrust reverser that must be alternately moved back and forth. In this example scenario, aircraft may include a hydraulic actuator in order to controllably move the thrust reverser.
While hydraulic actuators are useful in many circumstances, some hydraulic actuators may become undesirably expensive in terms of the cost of the hydraulic system, in terms of the space and/or weight of the hydraulic system and/or in terms of the maintenance required to insure that the hydraulic actuator is operational. For example, the hydraulic actuator associated with a thrust reverser must generally be capable of being activated quickly, such as in order to rapidly move the thrust reverser at the end of an aborted take-off. In order to be able to be activated quickly, however, the resulting hydraulic actuator system may become undesirably expensive in terms of cost, space, weight or the like.
As such, induction motors may be utilized instead of hydraulic actuators in some circumstances in order to reduce the cost, space requirements, weight requirements, maintenance demands or the like. An induction motor generally requires three-phase alternating current (AC) power at a fixed frequency. However, the three-phase AC power that is provided by aircraft power systems may not necessarily be at a fixed frequency and, in any event, may not be at the fixed frequency that an induction motor utilizes for most efficient operation. Instead, aircraft power systems may provide three-phase power having a frequency that may vary across a range, such as between 320 Hz and 800 Hz, albeit at a relatively constant or regulated voltage.
In order to fix the frequency of the three-phase power, a frequency converter may receive the variable frequency AC input signal and may generate a fixed frequency AC output signal. The frequency converter may include a plurality of large capacitors and a number, e.g., six, of rectifying diodes and transistors to generate the output power at a fixed frequency. Such frequency converters may have a high cost and may weigh more than is desired. Moreover, the switching frequencies of such frequency converters may be undesirably high. In addition, such frequency converters may be undesirably sensitive to electromagnetic interference (EMI) and lightning or may require a particular physical layout and cabling to address EMI sensitivity.